The present invention relates to exhaust gas recirculation (EGR) pintle valves for internal combustion engines; more particularly, to such valves which are inwardly-opening; and most particularly, to such a valve wherein drag on the valve pintle shaft is minimized during actuation thereof.
Pintle valves are well known for use in controlling flow of fluids, and especially gases. An important use is for recirculating a portion of the exhaust gas from an internal combustion engine into the intake manifold thereof.
Current gas flow valves wherein a valve head is inwardly withdrawn into a chamber from a valve seat typically include a valve pintle bushing pressed into a bore in a valve wall opposite the valve seat. Because of high operating pressures in the valve chamber, the wall containing the bushing is typically a removable plate which is bolted onto the valve body after the bushing and valve pintle/head are installed. Such a large plate typically is gasketed to minimize gas leakage. Due to necessary tight clearances for the pintle in the bushing and the plurality of other components common to current EGR control valves, misalignment of the pintle and head with respect to the valve seat is virtually inevitable. The valve head must center itself in the seat, thereby exerting torque on a misaligned bushing which causes frictional drag on the pintle shaft as it moves through the bushing. Further, a gas shield for preventing leakage of exhaust gas into the solenoid actuator, if not very highly aligned with the pintle shaft, causes addition drag on the shaft during actuation. Typically, such parasitic losses require that a solenoid actuator for a prior art valve be undesirably large and power-consuming.
Further, such misalignments can result in significant leakage of gases to the exterior of the valve, whereas government regulations on emission are becoming ever stricter.
What is needed in the art is a means for allowing a pintle shaft bushing and a shaft gas seal to be radially floating and therefore self-aligning to reduce the power required to actuate the valve and to reduce emissions from the valve.
It is a principal object of the present invention to reduce the power required to operate an EGR valve by reducing frictional losses of actuation within the valve mechanism.
It is a further object of the present invention to reduce exhaust leakage from an EGR valve.
It is a still further object of the present invention to reduce the number of components of an EGR valve and to simplify assembly thereof.
Briefly described, a pintle-type valve in accordance with the invention includes a valve body enclosing a chamber. A first port surrounded by an annular valve seat is provided in a first wall of the body. A second port is formed in a second and opposite wall of the body coaxially with the first port for receiving a pintle bushing from outside the valve body. A valve pintle shaft, having an attached valve head for mating with the valve seat, is disposed in a close-fitting central bore in the bushing. The second port has a diameter larger than the diameter of the valve head, so that the valve head may be admitted to the chamber through the port. The bushing is radially floating in the port, has a flange extending along an outer surface of the valve body for forming a seal therewith, and is approximately centered and retained by a bushing retainer. The pintle extends into a conventional solenoid-type actuator which is attached to the valve body. A radially-floating gas seal surrounds the pintle between the retainer and the actuator. A compressed coil spring surrounding the pintle between the gas seal and the bushing holds the bushing in place against operating pressure within the valve chamber.